Secretion of growth hormone is increased by various physiologic stimuli and pharmacologic agents. With the recently developed radioimmunoassay for canine growth hormone it is now possible to study in the dog the mechanism of growth hormone release and to correlate changes in plasma growth hormone levels with appropriate sensitive metabolic measurements. Since growth hormone release appears to be influenced by central sympathetic neurohumoral mediation, selective adrenergic agonists and blocking agents will be administered to normal dogs and their influence on growth hormone release will be determined. The release of ACTH will be monitored as an additional reference point for the specificity of the growth hormone response. In addition various radioactive tracers will be used to determine the concomitant changes in the rates of hepatic glucose output and overall glucose utilization and in free fatty acid production and uptake.